Power train for an amphibian

ABSTRACT

The present invention provides a power train for an amphibian operable in land and marine modes. The power train including a prime mover, a first land propulsion device, a first marine propulsion device, and a speed change transmission, wherein the prime mover is arranged to drive the first land propulsion device via the speed change transmission in land mode, and at least a portion of the prime mover is located between the speed change transmission and a rearward most part of the amphibian, with the speed change transmission located spaced ahead of the prime mover by a selected distance using one or more drive shaft(s).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/568,323, filed Oct. 20, 2017, entitled “POWERTRAIN FOR AN AMPHIBIAN,”which claims benefit to PCT Application No. PCT/GB2016/051110, filedApr. 21, 2016, entitled ‘A POWERTRAIN FOR AN AMPHIBIAN,” the entiredisclosures of which are incorporated herein.

BACKGROUND OF THE INVENTION

The present invention relates to a power train particularly suitable foruse in an amphibian capable of travel on land and water. Moreparticularly, the power train is suitable for use in a high speedamphibian with at least one retractable wheel and/or track drive, andwhich is capable of planing on water and high speed travel on land (onor off-road, in two or four wheel drive). The present invention alsorelates to an amphibian having such a power train.

Power trains for use in amphibians are known in the art. These generallyfall in into one of two categories. The first category comprises powertrains for use in displacement only amphibians having limited and slowon-water performance. These are generally automotive use power trainsmodified to provide drive to a marine propulsion device. The secondcategory is power trains for use in planing amphibians and which sufferfrom limited on-land performance. These are generally marine powertrains modified to provide drive to a wheel.

More recently, however, the applicant has developed power trains for usein a new class of high speed amphibians having at least one retractablewheel and which are capable of planing on water. Furthermore, these highspeed amphibians provide for good road handling when the amphibian isoperated on land (on or off-road, in two or four wheel drive).

There remains, however, a need to improve on these prior art powertrains by providing alternative configurations for the delivery of driveand power to the marine propulsion device(s) (e.g. one or more jetdrives, propellers, etc.) for use of the amphibian on water, and to theland propulsion device(s) (e.g. one or more wheels, track drives, etc.)for use of the amphibian on land, as well as improved packaging of thepower train. The need to retract wheels and/or wheel suspensionassemblies or track drives presents significant problems in terms ofpackaging, weight distribution and also in terms of how the resultingpower transmission pathways can be realized.

SUMMARY OF THE INVENTION

For purposes of description herein, the terms “upper,” “lower,” “right,”“left,” “rear,” “front,” “vertical,” “horizontal,” and derivativesthereof shall relate to the invention as oriented in FIG. 1. However, itis to be understood that the invention may assume various alternativeorientations, except where expressly specified to the contrary. It isalso to be understood that the specific devices and processesillustrated in the attached drawings, and described in the followingspecification are simply exemplary embodiments of the inventive conceptsdefined in the appended claims. Hence, specific dimensions and othercharacteristics relating to the embodiments disclosed herein are not tobe considered as limiting, unless the claims expressly state otherwise.

In a first aspect, the present invention provides a power train for anamphibian operable in land and marine modes, the power train comprising:

a prime mover;

a first land propulsion device;

a first marine propulsion device; and

a speed change transmission, wherein:

the prime mover is arranged to drive the first land propulsion devicevia the speed change transmission in land mode; and

at least a portion of the prime mover is located between the speedchange transmission and a rearward most part of the amphibian, with thespeed change transmission located spaced ahead of the prime mover by aselected distance using one or more drive shaft(s).

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims and appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described byway of example only with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic plan view from above of a power train according toa preferred embodiment the present invention;

FIG. 2 is a schematic plan view from above of the power train of FIG. 1located in the hull of an amphibian, with certain components (e.g.wheels) omitted for clarity; and

FIG. 3 is a schematic side elevation view of the power train of FIGS. 1and 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to FIGS. 1 to 3, power train 10 can be seen to comprise:

a prime mover, engine 12;

a prime mover output drive shaft 13;

a variable speed change transmission 14;

a variable speed change transmission output drive shaft 15;

a transfer case 16;

two land propulsion drive shafts, front land propulsion drive shaft 26,and rear land propulsion drive shaft 32 formed of first shaft portion 28and second shaft portion 30;

two differentials, front differential 34 and rear differential 36;

four half (axle) shafts, port and starboard front half shafts 38, 40 andport and starboard rear half shafts 42, 44;

four wheels, port and starboard front wheels 46, 48 and port andstarboard rear wheels 50, 52;

power take-off 50;

two marine propulsion drive shafts, port water jet drive shaft 22 andstarboard water jet drive shaft 24; and

two marine propulsion units, port water jet drive 18 and starboard waterjet drive 20.

The prime mover 12 generates drive and power and transmits this on viathe prime mover output drive shaft 13. The prime mover 12 may be of anysuitable type. In this particular embodiment, the prime mover 12 is acompression ignition internal combustion engine. Drive shaft 13 leadsdrive and power from the prime mover 12 to, inter alia, the variablespeed change transmission 14, with drive shaft 13 serving as an inputdrive shaft to the variable speed change transmission 14. Drive shaft 13may optionally comprise drive shaft portions (as shown in FIGS. 1 to 3)coupled together via coupling 62, with provision for relativearticulation therebetween (e.g. by way of a universal or other likejoint), to provide flexibility in packaging and operation. The variablespeed change transmission 14 may comprise a manual, sequential shift,semiautomatic or automatic gearbox, continuously variable transmission(CVT), or any suitable variable speed change transmission. The variablespeed change transmission output drive shaft 15 leads drive and power(subjected to any speed change function) from the variable speed changetransmission 14 to a transfer case 16, with drive shaft 15 serving as aninput drive shaft to transfer case 16. The transfer case 16 is shown infront (ahead) of the variable speed change transmission 14 and mountedthereto, but could be spaced to the front of the variable speed changetransmission 14. The prime mover 12 and the variable speed changetransmission 14 are arranged spaced from one another. In this particularembodiment, they are arranged longitudinally in the amphibian, generallyaligned with a longitudinal axis X-X of the hull 100 of the amphibian(see FIG. 2), but not necessarily on a centreline, with the variablespeed change transmission 14 being mounted forward (ahead) of the primemover 12. By using drive shaft 13, rather than mounting the variablespeed change transmission 14 directly to the prime mover 12, thedistance between the variable speed change transmission 14 and the primemover 12 can be selected (increased or reduced) depending on therequirements of the amphibian, for example to suit the particularpackaging requirements of the amphibian and/or to optimize its balance.In such a case, the respective lengths of drive shafts can be selectedaccordingly to suit. As shown in this particular embodiment, at least aportion of prime mover 12 is arranged rearward (aft) of the reardifferential 36. More preferably, the prime mover 12 is arrangedrearward (aft) of the rear differential 36. In addition, oralternatively, at least a portion of variable speed change transmission14 is arranged forward (ahead) of the rear differential 36. Morepreferably, the variable speed change transmission 14 is arrangedforward (ahead) of the rear differential 36.

Transfer case 16 transfers drive from the drive shaft 15 to the frontand rear land propulsion drive shafts 26, 32 (drive shaft 32 beingformed of drive shaft portions 28 and 30 coupled together). The ratio ofdrive between drive shaft 15 and drive shafts 26, 32 is 1:1 but may beanother ratio (or a variable ratio) selected to suit the particulararrangement or operating conditions.

The front land propulsion drive shaft 26 leads drive and power from thetransfer case 16 forwards (ahead) in the amphibian to the frontdifferential 34. In turn, the front differential 34 provides drive toport front half shaft 38 and starboard front half shaft 40, and on torespective port front wheel 46 and starboard front wheel 48. As shown,the front differential 34 is generally aligned with a centrallongitudinal axis X-X of the hull 100 to allow for optimum packaging ofthe land propulsion protraction/retraction assemblies, optimizingarticulation on retraction. However, the front differential 34 may bearranged spaced laterally of a central longitudinal axis X-X of the hull100 to provide flexibility.

The rear land propulsion drive shaft 32 (drive shaft 32 being formed ofdrive shaft portions 28 and 30 coupled together) runs rearwardly (aft)in the amphibian from the transfer case 16 to the rear differential 36in order to transmit drive to the rear differential 36. In turn, therear differential 36 provides drive to port rear half shaft 42 andstarboard rear half shaft 44, and on to respective port rear wheel 50and starboard rear wheel 52. The first and second drive shaft portions28 and 30 are coupled together via coupling 60 with provision forrelative articulation therebetween (e.g. by way of a universal, hooker,CV, or other like joint) and together extend between the transfer case16 and the rear differential 34, arranged around the variable speedchange transmission 14. As shown, first drive shaft portion 28 is spacedlaterally from a central longitudinal axis X-X of the hull 100, withsecond drive shaft portion 30 arranged at an angle thereto towards acentral longitudinal axis X-X of the hull 100 to allow the second driveshaft portion 30 to connect with, and drive, the rear differential 36.The angle at which the coupling 60 connects the drive shaft portions 28,30 is selected based on the packaging requirements of the amphibian. Inan alternative arrangement, the first drive shaft portion 28 may bespaced above or below the variable speed change transmission 14 toprovide flexibility. As with front differential 34, rear differential 36is generally aligned with a central longitudinal axis X-X of the hull100 to allow for optimum packaging of the land propulsionprotraction/retraction assemblies, optimizing articulation onretraction. However, rear differential 36 may be arranged spacedlaterally of a central longitudinal axis X-X of the hull 100 to provideflexibility. Second drive shaft portion 30 may optionally comprise driveshaft portions (as shown in FIGS. 1 to 3) coupled together via coupling62, with provision for relative articulation therebetween (e.g. by wayof a universal or other like joint), to provide flexibility in packagingand operation.

The front and rear differentials 34, 36 transmit drive to the respectivefront and rear wheels 46, 48, 50, 52 of the amphibian via half (axle)shafts 38, 40, 42, 44 in a conventional automotive manner. Constantvelocity (CV) joints may be used as appropriate.

To enable drive from the prime mover 12 to the front and rear wheels 46,48, 50, 52 to be selectively decoupled, for example when the vehicle isin marine mode, the variable speed change transmission can be put inneutral. Alternatively, for added flexibility, a rear decoupler (notshown) may be provided between the rear land propulsion drive shaft 32and the rear differential 36 to enable drive from the prime mover 12 tothe rear differential 36 to be selectively decoupled, for example whenthe vehicle is in marine mode. Similarly, a front decoupler (not shown)may be provided between the front land propulsion drive shaft 26 and thefront differential 34 to enable drive from the prime mover 12 to thefront differential 34 to be selectively decoupled in a similar manner tothat described above for the rear differential.

Decouplers may also be provided in the drive line between any/some/allof the various components, for example between wheels 46, 48, 50, 52 andits associated driving half shaft 38, 40, 42, 44, and/or betweenany/some/all of driving half shaft 38, 40, 42, 44 and respective frontand/or rear differentials 34, 36 to enable drive from the prime mover 12to the wheels 46, 48, 50, 52 to be selectively coupled and decoupled atwill. However, all such decouplers are not essential and can be omitted,or selected ones can be omitted. Where present, any suitable decouplerand associated actuation/control system may be employed. Constantvelocity joints may be provided as necessary to provide tolerance forangular differences between components in the power train 10. Inaddition, constant velocity joints may be beneficially employed in wheelretraction for use of the amphibian on water in high speed planing modeand/or for steering.

Power take-off 50 is located at a position forward (ahead) of, andmounted to the front of, the prime mover 12. Alternatively, the powertake-off 50 may be located at a position spaced forward (ahead) of, ormounted to the rear of, or spaced rearward (aft) of the prime mover 12.Power take-off 50 transfers drive and power from the output drive shaft13 (or, alternatively a further drive shaft cooperating with drive shaft13) to the port water jet drive shaft 22, via port belt 23, and to thestarboard water jet drive shaft 24, via starboard belt 25. Powertake-off 50 transfers drive and power at a ratio of 1.5:1 (input:output)and may be of any suitable type, for example, a belt drive, chain drive,or gear drive. Alternatively, the ratio may be another ratio (or avariable ratio) selected to suit the particular arrangement or operatingconditions. Port water jet drive shaft 22 and starboard water jet driveshaft 24 are arranged generally parallel with, and offset laterallyfrom, a central longitudinal axis X-X of the hull 100. As shown, thesedrive shafts 22, 24 are offset laterally but arranged below (or directlyunder) the lowest point prime mover 12. Alternatively, they may beoffset laterally to an extent that they are arranged adjacent at least aportion of the prime mover 12, enabling at least a portion of the primemover to be arranged lower in the amphibian, indeed lower in the hull100 than these drive shafts 22, 24. This flexibility provides for theprime mover to be positioned lower in the amphibian and can lower thecentre of gravity of the amphibian and adjust the metacentric height.

Port and starboard jet drive shafts 22, 24 extend rearward (aft) of thepower take-off 50 to drive the impellers of port and starboard jetdrives 18, 20, respectively.

In use, the power train 10 according to the present invention isextremely flexible and versatile. It can be operated in numerousdifferent ways, these being selected by the amphibian's control systemsand/or by or with inputs from the driver. In land mode (includingingress to and egress from the water), the amphibian may be driven inone, two, three or four wheel drive, and with various combinations ofthe individual wheels selected to provide drive. The jet drives 18, 20are also driven in land mode. In marine mode, both water jets 18, 20provide marine propulsion while drive to the wheels is prevented byputting the variable speed change transmission in neutral and/ordecoupling of the decoupler(s). By way of example only, the followingtable indicates a number of the modes/options available in theparticular configuration shown in FIG. 1:

Mode Wheel WaterJet L Land 1 1 wheeldrive Front port46 Port 18 and stbd20 2 1 wheeldrive Front stbd48 Port 18 and stbd 20 3 1 wheeldrive Rearport50 Port 18 and stbd 20 4 1 wheeldrive Rear stbd52 Port 18 and stbd20 5 2 wheeldrive Front port46 Port 18 and stbd 20 Front stbd48 6 2wheeldrive Rear port50 Port 18 and stbd 20 Rear stbd52 7 2 wheeldriveFront port46 Port 18 and stbd 20 Rear port50 8 2 wheeldrive Front stbd48Port 18 and stbd 20 Rear stbd52 9 2 wheeldrive Front port46 Port 18 andstbd 20 Rear stbd52 10 2 wheeldrive Front stbd48 Port 18 and stbd 20Rear port50 11 4 wheeldrive Front port46 Port 18 and stbd 20 Frontstbd48 Rear port50 Rear stbd52 12 Ingress/Egress Front port46 Port 18and stbd 20 Front stbd48 13 Ingress/Egress Rear port50 Port 18 and stbd20 Rear stbd52 14 Ingress/Egress Any, some, all Port 18 and stbd 20 MMarine 15 Displacement None, any, some, all Port 18 and stbd 20 16Planing None Port 18 and stbd 20

Of course, further modes/options are available with otherconfigurations. The flexibility and versatility of the power train 10according to the present invention is thus readily appreciated from theabove.

Although the prime mover 12 and the variable speed change transmission14 are shown generally in line with a longitudinal axis of the hull 100of the amphibian, alternative configurations are equally possible. Forexample, the prime mover 12 may be arranged transversely, with suitablearrangement of the other components.

FIG. 2 shows a preferred hull 100 of an amphibian in which a power train10 according to the present invention (and particularly illustrated inFIGS. 1 and 3) is located.

Retractable wheel (and/or track drive) and suspension assemblies (notshown) as described in the applicant's patents and published patentapplications are particularly suitable for use with the power train 10of the present invention.

In the preferred embodiment shown in the Figures, the marine propulsionunits shown indicatively are water jets drives 18, 20, but screwpropellers or any other suitable marine propulsion means, system orcombination may be employed. Further, two marine propulsion units areshown in the Figures and described above, but alternatively just onemarine propulsion unit may be employed.

A universal or other suitable joint 62, 64 (e.g. hookes, or CV) isprovided in the drive shafts 13 and 30 to provide additional flexibilityin packaging. The angle at which the joints 62, 64 connect therespective shaft portions, and the lengths selected for the respectiveshaft portions, is based on the packaging requirements of the particularamphibian.

While decouplers have been described, components in the power train maybe provided or supplied with integral decouplers, disconnects or locks(e.g. diff-locks) which can be used as appropriate. Furthermore, driveshafts may be single entities or formed from combinations of shorterdrive shafts and/or stub shafts.

Whilst wheels have been described throughout as the land propulsionmeans, track drives or individual track drives (i.e. to replace a singlewheel) may be used as an alternative or in combination with wheels.

Although the transfer case and power take-off have been described ashaving belts, they may be of any suitable type, for example, a beltdrive, chain drive or gear drive.

Furthermore, the compression ignition internal combustion enginedescribed for the prime mover 12 may instead comprise a spark ignitioninternal combustion engine, or an electric, hydraulic, or hybrid engine.Indeed, more than one of any such/alternative prime mover may beemployed. A stealth mode may be incorporated where the prime moverlimits noise and heat emissions. For example, the prime mover mayincorporate motor generators which act as alternators to chargebatteries, which charge is then used to power the vehicle for periods oftime in a stealth mode.

Each feature disclosed in this specification (including the accompanyingclaims and drawings) may be replaced by alternative features serving thesame, equivalent or similar purpose, unless expressly stated otherwise.Thus, unless expressly stated otherwise, each feature disclosed is oneexample only of a generic series of equivalent or similar features. Inaddition, all of the features disclosed in this specification (includingthe accompanying claims, abstract and drawings), and/or all of the stepsof a method or process, may be combined in any combination, exceptcombinations where at least some of such features and/or steps aremutually exclusive. Accordingly, while different embodiments of thepresent invention have been described above, any one or more or all ofthe features described, illustrated and/or claimed in the appendedclaims may be used in isolation or in various combinations in anyembodiment. As such, any one or more feature may be removed, substitutedand/or added to any of the feature combinations described, illustratedand/or claimed. For the avoidance of doubt, any one or more of thefeatures of any embodiment may be combined and/or used separately in adifferent embodiment with any other feature or features from any of theembodiments.

Whereas the present invention has been described in relation to what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not limited to thedisclosed arrangements but rather is intended to cover variousmodifications and equivalent constructions included within the scope ofthe appended claims.

The invention claimed is:
 1. A power train for an amphibian operable inland and marine modes, the power train comprising: a prime mover; afirst land propulsion device; a first marine propulsion device; and aspeed change transmission, wherein: the prime mover is arranged to drivethe first land propulsion device via the speed change transmission inland mode; and at least a portion of the prime mover is located betweenthe speed change transmission and a rearward most part of the amphibian,with the speed change transmission located spaced ahead of the primemover by a selected distance using one or more drive shaft(s).
 2. Thepower train as claimed in claim 1, wherein the first land propulsiondevice comprises at least one rear wheel or rear track drive or pair ofrear wheels or pair of rear track drives.
 3. The power train as claimedin claim 1, wherein at least a portion thereof of the prime mover islocated spaced aft of the first land propulsion device.
 4. The powertrain as claimed in claim 1, wherein at least a portion of the speedchange transmission is located spaced ahead of the first land propulsiondevice.
 5. The power train as claimed in claim 1, wherein the powertrain further comprises a first differential connected to the speedchange transmission via a first land propulsion drive shaft, and whereinthe speed change transmission is arranged to drive the first landpropulsion device via the first land propulsion drive shaft and thefirst differential.
 6. The power train as claimed in claim 5, whereinthe first differential includes a rear differential and the first landpropulsion drive shaft includes a rear land propulsion drive shaft. 7.The power train as claimed in claim 1, wherein the power train furthercomprises one or more decouplers arranged to selectively decouple theprime mover from the first land propulsion device.
 8. The power train asclaimed in claim 1, the power train further comprising a second landpropulsion device, and wherein the prime mover is arranged to drive thesecond land propulsion device via the at least one speed changetransmission in land mode.
 9. The power train as claimed in claim 8,wherein the second land propulsion device comprises at least one frontwheel or front track drive or pair of front wheels or pair of fronttrack drives.
 10. The power train as claimed in claim 8, wherein thepower train further comprises a second differential connected to thespeed change transmission via a second land propulsion drive shaft, andwherein the speed change transmission is arranged to drive the secondland propulsion device via the second land propulsion drive shaft andthe second differential.
 11. The power train as claimed in claim 10,wherein the second differential includes a front differential and thesecond land propulsion drive shaft includes a front land propulsiondrive shaft.
 12. The power train as claimed in claim 1, the power trainfurther comprising a first transfer case or power take off arranged toreceive drive, when drive is provided, from the speed changetransmission.
 13. The power train as claimed in claim 12, wherein thespeed change transmission is arranged to drive the at least one of thefirst land propulsion device and the second land propulsion device viathe first transfer case or power take off.
 14. The power train asclaimed in claim 5, wherein at least a portion of the first landpropulsion drive shaft runs adjacent the speed change transmission,either to the side, above or below the speed change transmission. 15.The power train as claimed in claim 5, wherein the first land propulsiondrive shaft comprises a first shaft portion coupled to a second shaftportion, wherein the second shaft portion is arranged to transmit drivefrom the first shaft portion to the first differential.
 16. The powertrain as claimed in claim 15, wherein the second shaft portion iscoupled to the first shaft portion by a universal, a hooker or a CVjoint such that the longitudinal axis of the second shaft portion may bearranged at an angle to the longitudinal axis of the first shaftportion.
 17. The power train as claimed in claim 15, wherein the secondshaft portion is coupled to the first shaft portion by a belt drive, agear drive, a chain drive or other such arrangement such that thelongitudinal axis of the second shaft portion is offset laterally fromthe longitudinal axis of the first shaft portion, either substantiallyparallel or otherwise.
 18. The power train as claimed in claim 15,wherein the first shaft portion is coupled to the second shaft portionat a location in front of the prime mover.
 19. The power train asclaimed in claim 8, wherein the power train further comprises one ormore decouplers arranged to selectively decouple the prime mover fromthe second land propulsion device.
 20. The power train as claimed inclaim 7, further comprising control means to selectively activate anddeactivate any of the one or more decouplers in the power train.
 21. Thepower train as claimed in claim 1, wherein the prime mover is arrangedto drive, when drive is provided, the first marine propulsion device viaa first marine propulsion drive shaft.
 22. The power train as claimed inclaim 21, wherein the power train comprises a second marine propulsiondevice and the prime mover is arranged to drive, when drive is provided,the second marine propulsion device via a second marine propulsion driveshaft.
 23. The power train as claimed in claim 21, wherein the powertrain further comprises a second power take off or transfer casearranged to receive drive directly from the prime mover, the secondpower take off or transfer case arranged to drive, when drive isprovided, the first and/or a second marine propulsion drive shaft. 24.The power train as claimed in claim 23, wherein the second power takeoff or transfer case is arranged to selectively alter the transmissionratio between the prime mover and a third marine propulsion shaft. 25.The power train as claimed in claim 1, wherein the prime mover comprisesany one or combination of a spark ignition internal combustion engine, acompression ignition internal combustion engine, an electric motor, ahydraulic motor, a hybrid engine, or a motor generator.
 26. The powertrain as claimed in claim 1, wherein either one or both of the firstmarine propulsion device and a second marine propulsion device compriseeither a water jet, or a propeller.
 27. The power train according toclaim 1, wherein the speed change transmission comprises a variablespeed change transmission.
 28. The power train according to claim 1,wherein the speed change transmission comprises any one or more of amanual, sequential shift, semiautomatic, or automatic gearbox, or acontinuously variable transmission.
 29. The power train as claimed inclaim 5, wherein the prime mover, or at least a portion thereof, islocated spaced aft of, behind, the first differential.
 30. The powertrain as claimed in claim 5, wherein the speed change transmission, orat least a portion thereof, is located spaced ahead of the firstdifferential.
 31. An amphibian comprising the power train of claim 1.32. The amphibian as claimed in claim 31, wherein the prime mover ispositioned substantially in line with a longitudinal axis of theamphibian.
 33. The amphibian as claimed in claim 31, wherein the speedchange transmission is located in front of the prime mover.
 34. Theamphibian as claimed in claim 31, wherein the first and/or a second landpropulsion device may be retracted above the lowest point of the hullfor use on water in marine mode, and may be protracted below the lowestpoint of the hull for use on land in land mode.
 35. The amphibian asclaimed in claim 31, wherein when the amphibian is operated in a marinemode the first and/or a second marine propulsion device can power theamphibian to a speed where sufficient hydrodynamic lift is achieved forthe amphibian to plane.
 36. The amphibian as claimed in claim 31,wherein when the amphibian is operated in a land mode it can be drivenin one, two, three or four wheel drive.